Histone deacetylase inhibitor trichostatin A sensitises cisplatin-resistant ovarian cancer cells to oncolytic adenovirus

Sindbis Virus Vaccine Platform: A Promising Oncolytic Virus-Mediated Approach for Ovarian Cancer Treatment

This review article provides a comprehensive overview of a novel Sindbis virus vaccine platform as potential immunotherapy for ovarian cancer patients. Ovarian cancer is the most lethal of all gynecological malignancies. The majority of high-grade serous ovarian cancer (HGSOC) patients are diagnosed with advanced disease. Current treatment options are very aggressive and limited, resulting in tumor recurrences and 50-60% patient mortality within 5 years. The unique properties of armed oncolytic Sindbis virus vectors (SV) in vivo have garnered significant interest in recent years to potently target and treat ovarian cancer. We discuss the molecular biology of Sindbis virus, its mechanisms of action against ovarian cancer cells, preclinical in vivo studies, and future perspectives. The potential of Sindbis virus-based therapies for ovarian cancer treatment holds great promise and warrants further investigation. Investigations using other oncolytic viruses in preclinical studies and clinical trials are also presented.

Histone deacetylase inhibitor boosts anticancer potential of fusogenic oncolytic vaccinia virus by enhancing cell-cell fusion

Oncolytic viruses have two anticancer functions: direct oncolysis and elicitation of antitumor immunity. We previously developed a novel fusogenic oncolytic vaccinia virus (FUVAC) from a non-fusogenic vaccinia virus (VV) and, by remodeling the tumor immune microenvironment, we demonstrated that FUVAC induced stronger oncolysis and antitumor immune responses compared with non-fusogenic VV. These functions depend strongly on cell-cell fusion induction. However, FUVAC tends to have decreased fusion activity in cells with low virus replication efficacy. Therefore, another combination strategy was required to increase cell-cell fusion in these cells. Histone deacetylase (HDAC) inhibitors suppress the host virus defense response and promote viral replication. Therefore, in this study, we selected an HDAC inhibitor, trichostatin A (TSA), as the combination agent for FUVAC to enhance its fusion-based antitumor potential. TSA was added prior to FUVAC treatment of murine tumor B16-F10 and CT26 cells. TSA increased the replication of both FUVAC and parental non-fusogenic VV. Moreover, TSA enhanced cell-cell fusion and FUVAC cytotoxicity in these tumor cells in a dose-dependent manner. Transcriptome analysis revealed that TSA-treated tumors showed altered expression of cellular component-related genes, which may affect fusion tolerance. In a bilateral tumor-bearing mouse model, combination treatment of TSA and FUVAC significantly prolonged mouse survival compared with either treatment alone or in combination with non-fusogenic VV. Our findings demonstrate that TSA is a potent enhancer of cell-cell fusion efficacy of FUVAC.

HDAC Inhibitors Enhance Efficacy of the Oncolytic Adenoviruses Ad∆∆ and Ad-3∆-A20T in Pancreatic and Triple-Negative Breast Cancer Models

The prognosis for triple-negative breast cancer (TNBC) and pancreatic ductal adenocarcinoma (PDAC) is dismal. TNBC and PDAC are highly aggressive cancers with few treatment options and a potential for rapid resistance to standard-of-care chemotherapeutics. Oncolytic adenoviruses (OAds) represent a promising tumour-selective strategy that can overcome treatment resistance and eliminate cancer cells by lysis and host immune activation. We demonstrate that histone deacetylase inhibitors (HDACi) potently enhanced the cancer-cell killing of our OAds, Ad∆∆ and Ad-3∆-A20T in TNBC and PDAC preclinical models. In the TNBC cell lines MDA-MB-436, SUM159 and CAL51, cell killing, viral uptake and replication were increased when treated with sublethal doses of the Class-I-selective HDACis Scriptaid, Romidepsin and MS-275. The pan-HDACi, TSA efficiently improved OAd efficacy, both in vitro and in SUM159 xenograft models in vivo. Cell killing and Ad∆∆ replication was also significantly increased in five PDAC cell lines when pre-treated with TSA. Efficacy was dependent on treatment time and dose, and on the specific genetic alterations in each cell line. Expression of the cancer specific αvß6-integrin supported higher viral uptake of the integrin-retargeted Ad-3∆-A20T in combination with Scriptaid. In conclusion, we demonstrate that inhibition of specific HDACs is a potential means to enhance OAd activity, supporting clinical translation.

Histone modifiers at the crossroads of oncolytic and oncogenic viruses

Cancer is a disease caused by loss of regulatory processes that control cell cycle, resulting in increased proliferation. The loss of control can deregulate both tumor suppressors and oncogenes. Apart from cell intrinsic gene mutations and environmental factors, infection by cancer-causing viruses also induces changes that lead to malignant transformation. This can be caused by both expression of oncogenic viral proteins and also by changes in cellular genes and proteins that affect the epigenome. Thus, these epigenetic modifiers are good therapeutic targets, and several epigenetic inhibitors are approved for the treatment of different cancers. In addition to small molecule drugs, biological therapies such as antibodies and viral therapies are also increasingly being used to treat cancer. An HSV-1 derived oncolytic virus is currently approved by the US FDA and the European Medicines Agency. Similarly, an adenovirus-based therapeutic is approved for use in China for some cancer types. Since viruses can affect cellular epigenetics, the interaction of epigenome-targeting drugs with oncogenic and oncolytic viruses is a highly significant area of investigation. Here we will review the current knowledge about the impact of using epigenetic drugs in tumors positive for oncogenic viruses or as therapeutic combinations with oncolytic viruses.

Carvedilol targets β-arrestins to rewire innate immunity and improve oncolytic adenoviral therapy

Oncolytic viruses are being tested in clinical trials, including in women with ovarian cancer. We use a drug-repurposing approach to identify existing drugs that enhance the activity of oncolytic adenoviruses. This reveals that carvedilol, a β-arrestin-biased β-blocker, synergises with both wild-type adenovirus and the E1A-CR2-deleted oncolytic adenovirus, dl922-947. Synergy is not due to β-adrenergic blockade but is dependent on β-arrestins and is reversed by β-arrestin CRISPR gene editing. Co-treatment with dl922-947 and carvedilol causes increased viral DNA replication, greater viral protein expression and higher titres of infectious viral particles. Carvedilol also enhances viral efficacy in orthotopic, intraperitoneal murine models, achieving more rapid tumour clearance than virus alone. Increased anti-cancer activity is associated with an intratumoural inflammatory cell infiltrate and systemic cytokine release. In summary, carvedilol augments the activity of oncolytic adenoviruses via β-arrestins to re-wire cytokine networks and innate immunity and could therefore improve oncolytic viruses for cancer patient treatment.

GM101 in Combination with Histone Deacetylase Inhibitor Enhances Anti-Tumor Effects in Desmoplastic Microenvironment

Oncolytic adenoviruses (oAds) have been evaluated in numerous clinical trials due to their promising attributes as cancer therapeutics. However, the therapeutic efficacy of oAds was limited due to variable coxsackie and adenovirus receptor (CAR) expression levels and the dense extracellular matrix (ECM) of heterogenic clinical tumors. To overcome these limitations, our present report investigated the therapeutic efficacy of combining GM101, an oAd with excellent tumor ECM degrading properties, and histone deacetylase inhibitor (HDACi). Four different HDACi (suberohydroxamic acid (SBHA), MS-275, trichostatin A (TSA), and valproic acid) candidates in combination with replication-incompetent and GFP-expressing Ad (dAd/GFP) revealed that SBHA and MS-275 exerted more potent enhancement in Ad transduction efficacy than TSA or valproic acid. Further characterization revealed that SBHA and MS-275 effectively upregulated CAR expression in cancer cells, improved the binding of Ad with cancer cell membranes, and led to dynamin 2- and clathrin-mediated endocytosis of Ad. The combination of GM101 with HDACi induced superior cancer cell killing effects compared to any of the monotherapies, without any additional cytotoxicity in normal cell lines. Further, GM101+SBHA and GM101+MS-275 induced more potent antitumor efficacy than any monotherapy in U343 xenograft tumor model. Potent antitumor efficacy was achieved via the combination of GM101 with HDACi, inducing necrotic and apoptotic cancer cell death, inhibiting cancer cell proliferation, degrading ECM in tumor tissue, and thus exerting the highest level of virus dispersion and accumulation. Collectively, these data demonstrate that the combination of GM101 and HDACi can enhance intratumoral dispersion and accumulation of oAd through multifaced mechanisms, making it a promising strategy to address the challenges toward successful clinical development of oAd.

Hitting the Target but Missing the Point: Recent Progress towards Adenovirus-Based Precision Virotherapies

More people are surviving longer with cancer. Whilst this can be partially attributed to advances in early detection of cancers, there is little doubt that the improvement in survival statistics is also due to the expansion in the spectrum of treatments available for efficacious treatment. Transformative amongst those are immunotherapies, which have proven effective agents for treating immunogenic forms of cancer, although immunologically "cold" tumour types remain refractive. Oncolytic viruses, such as those based on adenovirus, have great potential as anti-cancer agents and have seen a resurgence of interest in recent years. Amongst their many advantages is their ability to induce immunogenic cell death (ICD) of infected tumour cells, thus providing the alluring potential to synergise with immunotherapies by turning immunologically "cold" tumours "hot". Additionally, enhanced immune mediated cell killing can be promoted through the local overexpression of immunological transgenes, encoded from within the engineered viral genome. To achieve this full potential requires the development of refined, tumour selective "precision virotherapies" that are extensively engineered to prevent off-target up take via native routes of infection and targeted to infect and replicate uniquely within malignantly transformed cells. Here, we review the latest advances towards this holy grail within the adenoviral field.

Pt(IV) pro-drugs with an axial HDAC inhibitor demonstrate multimodal mechanisms involving DNA damage and apoptosis independent of cisplatin resistance in A2780/A2780cis cells

Epigenetic agents such as histone deacetylase (HDAC) inhibitors are widely investigated for use in combined anticancer therapy and the co-administration of Pt drugs with HDAC inhibitors has shown promise for the treatment of resistant cancers. Coordination of an HDAC inhibitor to an axial position of a Pt(IV) derivative of cisplatin allows the combination of the epigenetic drug and the Pt chemotherapeutic into a single molecule. In this work we carry out mechanistic studies on the known Pt(IV) complex cis,cis,trans-[Pt(NH₃)₂Cl₂(PBA)₂] (B) with the HDAC inhibitor 4-phenylbutyrate (PBA) and its derivatives cis,cis,trans-[Pt(NH₃)₂Cl₂(PBA)(OH)] (A), cis,cis,trans-[Pt(NH₃)₂Cl₂(PBA)(Bz)] (C), and cis,cis,trans-[Pt(NH₃)₂Cl₂(PBA)(Suc)] (D) (Bz = benzoate, Suc = succinate). The comparison of the cytotoxicity, effect on HDAC activity, reactive oxygen species (ROS) generation, γ-H2AX (histone 2A-family member X) foci generation and induction of apoptosis in cisplatin-sensitive and cisplatin-resistant ovarian cancer cells shows that A - C exhibit multimodal mechanisms involving DNA damage and apoptosis independent of cisplatin resistance.

Genome-wide CRISPR-Cas9 screening reveals ubiquitous T cell cancer targeting via the monomorphic MHC class I-related protein MR1

Human leukocyte antigen (HLA)-independent, T cell-mediated targeting of cancer cells would allow immune destruction of malignancies in all individuals. Here, we use genome-wide CRISPR-Cas9 screening to establish that a T cell receptor (TCR) recognized and killed most human cancer types via the monomorphic MHC class I-related protein, MR1, while remaining inert to noncancerous cells. Unlike mucosal-associated invariant T cells, recognition of target cells by the TCR was independent of bacterial loading. Furthermore, concentration-dependent addition of vitamin B-related metabolite ligands of MR1 reduced TCR recognition of cancer cells, suggesting that recognition occurred via sensing of the cancer metabolome. An MR1-restricted T cell clone mediated in vivo regression of leukemia and conferred enhanced survival of NSG mice. TCR transfer to T cells of patients enabled killing of autologous and nonautologous melanoma. These findings offer opportunities for HLA-independent, pan-cancer, pan-population immunotherapies.

Oncolytic adenovirus Ad11 enhances the chemotherapy effect of cisplatin on osteosarcoma cells by inhibiting autophagy

Targeted oncolytic adenoviruses can selectively replicate in cancer cells; combined with traditional chemotherapy drugs, this approach is expected to become an important treatment method for overcoming the current bottleneck of osteosarcoma treatment. Here, we investigate the effect of oncolytic adenovirus Ad11 combined with cisplatin on autophagy in osteosarcoma cells. Immunohistochemistry was used to detect CD46 expression in patients with osteosarcoma. A cytotoxicity assay was employed to detect the killing effect of Ad11, cisplatin and their combination on osteosarcoma cells under different time scenarios. Expression of autophagy proteins Beclin1, ATG3, and LC3A/B under treatment of osteosarcoma cells with Ad11, cisplatin and their combination under different time scenarios was detected by immunofluorescence and western blotting. We found that the oncolytic adenovirus Ad11 synergizes with cisplatin to kill osteosarcoma cells and that the synergistic effect was greatest when cells were first treated with Ad11. This synergy is due to oncolytic adenovirus Ad11-mediated inhibition of autophagy, which enhanced the sensitivity of cells to chemotherapy. In conclusion, this study provides evidence that the oncolytic adenovirus Ad11 can enhance the effect of chemotherapy by inhibiting autophagy. The findings provide a cytological basis for the treatment of osteosarcoma with oncolytic adenovirus combined with cisplatin.

Overexpression of Adenoviral E1A Sensitizes E1A+Ras-Transformed Cells to the Action of Histone Deacetylase Inhibitors

The adenoviral E1A protein induces cell proliferation, transformation, and tumor formation in rodents, on the one hand. On the other hand, E1A expression increases cell sensitivity to a number of cytotoxic agents. Therefore, E1A is a candidate for use as a component of combination therapy for malignant tumors. The highest augmentation in the cytotoxic effect was achieved by a combined use of E1A expression and histone deacetylases (HDAC) inhibitors. However, HDAC inhibitors do not induce apoptosis in cells transformed with E1A and cHa-ras oncogenes. In this study, it was shown that HDAC inhibitors reduce the expression of adenoviral E1A. However, under unregulated E1A overexpression, these cells undergo apoptosis in the presence of HDAC inhibitors. Treatment with a HDAC inhibitor, sodium butyrate (NaBut), was shown to activate the anti-apoptotic factor NF-kB in control cells. However, NaBut was unable to modulate the NF-kB activity in E1A overexpressed cells. Therefore, it is fair to postulate that cells transformed with E1A and cHa-ras oncogenes avoid the apoptosis induced by HDAC inhibitors thanks to a NaBut-dependent decrease in E1A expression.